An infant has no consciousness of either reality or unreality. He has simply conscious states, without any such distinction. But he cannot fail to learn the distinction. He is hungry. He cries. He becomes conscious of reproduced former experiences of food and of the mother bringing the food. And, indeed, the door opens, the mother enters with the food, very similar to the imagined mother, and yet differing in vividness, in permanence, in number of details. At a later time the child imagines strange compositions: animals with legs both below and on their backs, so that they can turn over and continue running when one set of legs is tired; princes and princesses with golden crowns on their heads; fairies carrying marvelous gifts in their hands. But nothing of this kind appears with the vividness, permanence, and distinctness characteristic of the mother entering the door. Human beings who appear with a similar vividness, permanence, and distinctness, either are bareheaded or wear plain-looking hats; and their gifts amount to but little. When the child imagines the experience with his mother, he recalls the substitution of the vivid and stable consciousness for the feeble and fleeting image of the mother and the food. When he imagines his dreams of princes and fairies, he recalls the substitution of those vivid but homely mental states for less vivid but more beautiful ones. When such experiences have been repeated hundreds of times, the child begins to realize that there is a distinction of the greatest importance between the two classes. He forms the abstract concepts of sensory perception and of fancy--of consciousness of various sensory qualities and characterized by indescribable vividness, permanence, and distinctness; and on the other hand, of consciousness of various sensory qualities and characterized by feebleness, fleetingness, and vagueness, and in this respect flatly contradicted by the mental states of the other kind. _In these abstract conceptions consists the consciousness of reality and unreality._ Reality and unreality are not logical opposites, but merely relative concepts.